1. Field of Invention
The present invention relates generally to electric power generators, and in particular to resonant thermoelectric generators.
2. Prior Art—Historical Discoveries
Three solid-state thermoelectric effects are well-known to those skilled in the physical sciences. They are the Seebeck effect, discovered by Thomas Johann Seebeck in 1826, the Peltier effect, discovered by J.C.A. Peltier in 1834, and the Thomson effect, discovered by William Thomson (Lord Kelvin) in 1854.
Seebeck discovered that if the ends of two dissimilar metal conductors are joined and the ends are subjected to different temperatures, a voltage arises that is proportional to the temperature difference. This voltage is measured by breaking one of the conductors and inserting a sensitive voltmeter. This device, in wide use today, is called a thermocouple. The ability of a junction to produce a potential difference arises from differing densities of electrons within the two dissimilar metals.
The voltage developed in a thermocouple is very small, on the order of millivolts. This is sufficient for measurement of temperatures. A number of thermocouples can be combined in series to yield a thermopile that delivers a greater voltage in response to the same temperature gradient. Thermopiles are useful in devices ranging from laser power measurement systems and infrared cameras to power sources.
Peltier discovered that if a current is passed through a thermocouple, such as the one described above, the temperature of one junction increases and that of the other junction decreases.
Thomson discovered that when an electrical current is passed through a material while the material is subjected to a temperature gradient, heat is either evolved or absorbed, depending upon the nature of the material.
In all the above cases, the observed effects are related to temperature differences, or gradients, and electrical properties of materials such as metals and semiconductors. The temperature gradients induce direct-current (DC) electricity in the materials.
Depending upon the materials used, the primary charge carriers that produce the electrical effects can be electrons or holes (the absence of electrons in a lattice). In a metal, the primary charge carrier is electrons.
Semiconductors fall into two categories: n-type and p-type. The terms n-type and p-type refer to the kind of charge carrier that is implanted or diffused within the semiconductor during its manufacture. For example, silicon is first purified then a small amount of antimony is added to provide an excess of electrons within the resulting material. This material is termed n-type because it contains an excess of negatively-charged electrons. Electrical charge is transported within the material by the electrons. On the other hand, when boron is added to purified silicon, the resulting material is deficient in electrons. Electrical charge in this material is carried by “holes”, i.e., mobile regions in the material that lack electrons and therefore carry a positive electrical charge.